Complex lubricant



United States Patent 3,155,619 COMPLEX LUBRICANT Martin M. McCormick,Chicago, Ill, assignor to Sinclair Research, 133C. Wilmington, Del., acorporation of Delaware No Drawing. Filed Feb. 12, 1962, Ser. No.172,783 8 Claims. (Cl. 252-39) This invention relates to a method forpreparing high temperature lubricating compositions thickened to agrease consistency with a mixed salt-soap thickener. More particularly,the present invention relates to an improved method of manufacturingcalcium acetate-fatty soap greases which are smooth and homogeneous andhave a small spread between unwo-rked and worked penetrations.

The use of mixed salt-soap thickeners as grease thickeners is well knownin the art. In manufacture, these admixtures are generally subjected toa shearing force sufiioient to disperse the soap in the base oil to forma grease structure. The shearing action involves the application offorce in a plane and disperses the soap in an intimately orientatedlinear pattern. However, it has been found that if the shearing force issufficient to improve the texture of greases in which the mole ratio ofsalt/ soap is in excess of 3:1, the milling operation results in agrease having a very wide range between worked and unworked penetrationeven though the grease has a stable structure. This thixotropic spreadis undesirable from the standpoint of slumpability into dispensingequipment and the limited ability of the grease to properly feed tosurfaces requiring lubricating.

In brief, the present invention relates to a process for the preparationof smooth and homogeneous mixed saltsoap thickened greases having anacceptable low level of thixotropy and containing a molar ratioexceeding 3:1 of alkaline earth metal salt/ soap type greases byemploying a certain homogenizing sequence consisting essentially of aninitial relatively high shear rate processing suficient to obtain highlyefficient and improved dispersion of the.

thickener followed by a lower shear rate operation sufiicient to bringthe worked and unworked penetrations of the greases in close proximityto one another. The term homogenizing is intended to include any methodof subjecting the lubricant to shearing forces.

The mixed salt-soap thickeners of the invention can be formed by theneutralization with a metal base of a low molecular weight and a highermolecular weight carboxylic acid, for instance high molecular weightacids and intermediate molecular weight acids and combinations of thesame. Therefore, the mixed salt-soap thickener may be formed from eithera combination of (1) a low molecular weight acid and a high molecularweight acid, or (2) a low molecular weight acid and an intermediatemolecular weight acid, or (3) a low molecular weight acid, anintermediate molecular weight acid and a high molec ular weight acid, inwhich the mol ratio of low molecular weight acid to the other acidsemployed exceeds 3:1 and may he as high as :1 or more to be effectivelyutilized in the preparation of the present grease composition.

in the preparation of these mixed saltsoap thickeners, any suitableprocedure may be used, for instance, a coneutralizaiion, pro-forming orstep-wise method. In the coneutralization method, a mixture of the lowand high and/ or intermediate molecular weight acids is neutralized witha suitable base, particularly the hydroxide and/or carbonate of thedesired metals. This coneutralization step is generally carried out in agrease kettle in situ, in the liquid menstruum to which the complexthickener is to be applied in actual. use. For example, the mixed acidsmay be coneutralized in a portion or all of the lubricating oil formingthe dispersant of a grease to be thickened by the mixed salt-soapthickener. Coneutralization is possible in cases in which the salts havethe same metal constituent, and the menstruum is inert under theconditions of saponification or neutralization. The coneutralizedmaterial may be heated to temperatures of about 20" to 5-00 B,preferably less than about 350 F., in order to dehydrate the product.

The mixed salt-soap thickener may also he prepared by separatelypreforming at least a. portion of the high and/or intermediate molecularweight carboxylic acid salt, intimately mixing this salt with the lowmolecular eight salt and then heating, if necessary. This method is lessdesirable than coneutralization in situ and is perhaps most useful froma practical standpoint when different metals are employed in forming thedifferent salts.

In the step-wise method the high molecular weight acid is melted in thebase oil in the presence of the metal base and then the low and/orintermediate weight acids are added and the mixture is allowed to reactat a temperature sulficient to render the grease substantiallyanhydrous.

The soap-forming fatty component contemplated in this invention are thesaturated and unsaturated, naturally occurring or syntheticgrease-making carboxylic fatty acids and their esters such as thenaturally occurring or processed fats and oils which are in glycerideform, that are commonly known in the art and containing about 7 to 30carbon atoms. have from about 12 to 30 carbon atoms, preferably about 12to 22 carbon atoms per molecule, and have saponification values of fromabout 270 to 170. The fatty acids normally used in the manufacture ofconventional greases, particularly the saturated acids, are prefen'ed.Suitable fatty acids include lauric, myristic acid, palmitic acid,stearic acid, the various hydroxy stearic acids, oleic acid, arachidicacid, behenic acid and the like. Naturally oc curring fatty acids suchas fish oil acids, tallow acids,

which contain chiefly stearic acid, coconut oil acids, castor oil, etc.may also be utilized directly or after hydrogenation to decrease anyundesirably high degree of unsaturation. Mixtures of these highmolecular Weight fatty acids, e.g., hydrogenated fish oil acids witholeic acid, in any proportions, are also operable, as are fractionsobtained by distillation, extraction or crystallization.

The intermediate molecular weight monocarboxylic acids are thosestraight-chain, saturated fatty acids having from about 7 to 12 carbonatoms. Operable intermediate molecular weight carboxylic acids areexemplified by:

Caprylic, pelargonic, and capric acids are preferred. The intermediatemolecular weight carboxylic acids of even carbon chain lengths arenormally obtained by processing from naturally-occurring materials suchas coconut oils. Pelargonic acid is obtained as a by-product in theproduction or" azelaic acid by the ozonolysis of oleic acid.

Suitable low molecular weight acids include saturated and unsaturatedaliphatic monocarboxylic acids having about 1 to 4 carbon atoms, such asformic, acetic, propionic, furoic, acrylic and similar acids includingtheir hydroxy derivatives, such as lactic acid. Acetic acid isespecially preferred. The acetic acid can be glacial acetic acid or anaqueous solution of acetic acid. The con-- centration of acid in thesolution often varies from about 60 to 99.9 weight percent, and ispreferably about 7 weight percent. The use of a substituted acetic acidis In general, the higher fatty acids" not excluded, where suchmodification may be desirable. For example, chloro-acetic acid may beused to modify the structure of a grease made in accordance with theinvention.

The metal component of the thickener system of the invention is used ina form which can combine chemically with carboxylic acids to form saltsor soaps. Ordinarily the metal hydroxide is used. The choice of metalcomponent depends to a certain extent on the use to which the multiplesalt and soap thickener of the invention is to be put. The alkalineearth metal hydroxides or carbonates such as those of calcium, bariumand strontium are useful for many purposes of the invention. Calciumhydroxide or hydrated lime is especially preferred.

The lubrication oil may be either a mineral base lubricating oil orvarious synthetic oils. Mineral base lubricating oils ranging inviscosity from about 30l000 SSU at 100 F. are preferably employed as theliquid phase of the grease compositions of the invention. Thesenaturally occurring mineral lubricating oils may be derived from anypetroleum crude source, whether paratfinic or naphthcnic in type, andmay be refined by any of the known refining techniques of the petroleumindustry.

The invention is not limited, however, to the use of mineral base oils,since various synthetic oils having at least 30 Saybolt Universalviscosity at 100 F, may also be used as part or all of the liquid phaseof the grease. Examples of operable synthetic lubricating oils includeother alcohols, such as those corresponding to the general formulawherein R is an alkyl group, e.g., butyl, n is an integer from 2 to 5,and x is an integer from 1 to 40; esters of monobasic carboxylic acids,totalling 8 to 80 carbon atoms, such as those of C to C aliphatic acidswith C to C aliphatic alcohols, the C to C radicals including the butyl,isobutyl, hexyl, octyl, iso-octyl, 2-ethyl hexyl, nonyl, decyl, lauryl,stearyl and similar radicals; diesters of dibasic acids, such as adipicor sebacic acid with monohydric alcohols, such as hexyl, octyl, 2-ethy1hexyl or higher alcohols; esters of polyethylene glycols with C to Cbranched-chain carboxylic acids; complex esters of polybasic carboxylicacids, polyhydric alcohols, and monobasic acids and/or monohydricalcohols, such as the glycol-centered or dibasic acid-centered complexesters; phosphoric acid esters or thioesters of aliphatic al cohols ormercaptans of up to about 18 carbon atoms; halocarbon oils, such as thepolymers of chlorotluoro alkylenes like chlorotrhluoroethylene;organo-siloxanes; sulfite esters, organic carbonates; mercaptals;formals, etc.

In preparing the lubricating grease composition of this invention, about50 to 95 weight percent of lubricating oil and from about to 50 Weightpercent of the mixed salt-soap thickener may be used. A preferred rangeis from about 10 to 30 weight percent of the mixed salt-soap thickener,based on the weight of the total composition. This mixed salt-soapthickener, in turn, can be prepared by using 1 mole of the high and/orintermediate molecular weight acid with about 3 to or or more mols,preferably 5 to 12 mols of the low molecular weight acid withstoichiometric amounts of the metal base suilicient to react with theacids and other saponifiable components of the thickener system.

The greases may also contain various additives of the usual type such ascorrosion inhibitors, oxidation inhibitors, anti-wear agents, extremepressure agents, etc. The additive may be added either before or duringthe cooling down process. They are preferably added while thetemperature of the grease is between about 300 F. and about 180 F.

In general, the lubricating grease compositions can be made in any waydesired, for instance by mixing together the desired amount of mineralor synthetic lubricating oil, the base and the high molecular weightcarboxylic acid. The acetic acid and the intermediate molecular weightcarboxylic acid, if one is employed, are then added to the mixture, andallowed to react without further external heating. When temperature ofthe reaction starts to subside, external heating is then applied and iscontinued until the temperature is within the range of about 250-500" F.until the water content is below about 0.5 weight percent rendering thegrease substantially an hydrous. The exact temperature range which maybe used varies from one process to another depending upon differentprocedural steps fully understood by those skilled in the art. When themaximum temperature desired in reached, heating may be discontinued andthe grease batch is cooled to about 250 F. Any of the conventionalantioxidant additives, such as phenyl alpha naphthylarnine, may be addedat this time, and the grease is further cooled to below about 200 F. Theresulting grease composition is then homogenized by passing the greasethrough a suitable high shear rate milling device, such as for example,a Charlotte Colloid Mill, Mantin- Gaulin Homogenizer, Morehouse Mill,Cornell Deaerator and Turbinizer (Lancaster Dispenser) which haveshearing rates in the range of about 5000 to 500,000 reciprocal secondssuiiicient to complete the mixing operation in a short period of timeand obtain smooth, butterytexture grease. Before homogenization many ofthese greases have in addition to a rough texture a softer unworked thanworked consistency. The homogenizing operation results in a large amountof hardening of the greases on the basis of both worked and unworkedpenetration. Also, it has been found that when a mixed saltsoapthickened grease having a salt/soap ratio in excess of 3:1, ishomogenized under sufiicient shear rate to improve the greases texture,i.e. about 5000 to 500,000 reciprocal seconds, there will result a largespread between the unworked and worked consistency amounting to morethan an NLGI grade range. As mentioned above, this excessive spread isundesirable from the standpoint of slumpability and its ettectiveness tobe properly fed to surfaces requiring lubrication. However, thisundesirable penetration spread is essentially eliminated by the highshear-low shear homogenizing treatment of the pres ent invention.

The consistency of the grease is measured in terms of penetration at 77F. using an ASTM conical type penetrometer, for instance, ASTM methodD-217-60-T. The grease is mechanically worked in an ASTM grease worker,which consists essentially of a piston and cylinder assembly wherein thepiston is a disk having many relatively small perforations. The cylinderis charged with grease, and the piston reciprocated, thus rapidlyforcing the grease through the perforations. This penetration isgenerally measured before working and after 60 and 10,000 or 100,000full double strokes.

In the preparation of calcium acetate/soap greases having a molar ratioin excess of 3: 1, a suitable range for shearing is below about 225 F.,preferably below about 200 F. The initial homogenization applied to thecalcium acetate/soap greases is of sufiicient shear rate to obtainhighly etficient and improved dispersion of the thickener. This shearingon all or a substantial or major portion of the grease imparts to thegrease a consistency spread between unworked and worked penetrations at77 F. in the range of about 25 to mm./l0, usually about 30 to 60 mm./10.The second homegenization is again conducted on all or a substantial ormajor portion of the grease and is of low shear and brings the unworkedand worked penetrations of the greases to a range of about 015 mm./ 10,preferably about 0 to 10 mm./l0. In terms of shearing force the initialhomogenization should be in therange of about 5,000 to 500,000reciprocal seconds, preferably from about 10,000 to 200,000 reciprocalseconds. The low shearing rate should be in the range between about 1 to500 reciprocal seconds, preferably from about 1 to 300 reciprocalseconds. For instance, in the examples described below, the high shearrate used is about 75,000 reciprocal seconds and the low shear about 45reciprocal seconds. 1

In the process of the present invention it should be understood that thehigh shear rate treatment is not necessarily initial or the low shearrate second, it is, however, essential that the low shear treatmentfollows the high shear as a final step in the processing sequence. Forinstance, in the examples described below the grease is continuouslypassed from a low shear rate zone, the mixing kettle, through a highshear rate device, such as a Colloid Mill, and passed either back to thelow shear rate mixing zone or another suitable low shear rate device fora period of time suiiicient to obtain the above-mentioned desiredresults as the final step in the processing sequence.

The present invention will be more fully understood by reference to thefollowing specific examples which illustrate the processing method ofthe present invention.

EXAMPLE I Str-aight chain fatty acid having the following character- 1310s: I

Acid No. 240 Saponification No. 240 Iodine value 62 Average molecularweight 233 The grease was separated into four samples and tested interms of penetration at 77 F. using as ASTM conical type (low shearhomogenizing) for minutes, which corresponds to a complete turnover ofthe batch, the spread between the unworked and worked penetration isvery small while the grease still retains a smooth texture (Sample 93).

EXAMPLE II An 8:51 molar ratio calcium acetate/mixed fatty soap greasehaving the following composition was prepared. Component, lbs:

Glacial acetic acid 60.5 Vegetable fatty acid 18.25 Tallow fatty acid6.2 Hydrogenated castor oil 6.2 Hydrated lime 43.0 430 SUS/l00 F. M.C.neutral 410.0

The grease was treated as indicated in Table II.

Table II Calcium Acetate, Wt. Percent 15. 2 Calcium Soap, Wt. Percent 6.3 Moisture, Wt. Percent 0.6 Free 080, Wt. Percent-.. 0. 26

Sample No '96 96A 9613* Kettle Colloid Recycle Sample Milled Colloid(Unmilled) (Once Milled through) around the kettle ASTM Penetrations,mm./l0:

Unworked 306 233 297 Worked Strokes) 319 289 292 Recycled 25 minutesthrough colloid mill (Charlotte No. 3) at 0.005 clearance with an inlettemperature of F. and an outlet temperature of F. at a rate of 18lbs/minute. The grease is then mixed with pump recycle by-passing thecolloid mill for another 25 minutes. The samples were recovered at 168F.

EXAMPLE III penetrometer before and after certain homogenizing 40procedures. The results are tabulated in Table I. A 6:1 molar ratio ofcalcium acetate/ mixed fatty Table I Calcium Acetate, Wt. percent..-15.0 14.2 Calcium Soap, Wt. percent 8.2 7. 8 Moisture, Wt. percent 0.3Free CaO, Wt. percent 0.29

Sample N o 90 91- 92 92A 93* 95 Charlotte Recycle to Colloid RecycleKettle Kettle Cornell Mill & thru 001- thru 001- Oil added SampleDeaerator Cornell loid Mill loid Mill to 93 Deaerator' and DcaeratorAS'IM Penetrations, nnnJlO:

318 237 224 203 250 283 294 270 261 228 248 280 Texture Rough SmoothSmooth 7 Smooth Smooth Smooth *Recycled around kettle through colloidmill and deaerator for 45 minutes at 0.005 clearance at an inlettemperature of F. and a rate of lbs/min.

It is to be noted that the Kettle Sample (Sample 90) exhibitions a roughtexture and softer consistency unworked than worked. When the grease ishomogenized to obtain a smooth texture at high shear (Samples 91 and92), there results a large spread between the unworked and workedpenetrations. Even after a second pass through the high shearhomogenizer, the Colloid Mill (Sample 92A), there still exists a largespread'between unworked and worked penetrations. Also, after a highshear homogenizing the grease has a harder consistency unworked than itdoes worked. However, by recycling the grease through the homogenizerand back to the kettle soap grease having the following composition wasprepared.

Components, 1bs.:

Glacial acetic acid 48.0

The grease was treated as shown in Table III.

Recycled 20 minutes around kettle through colloid mill at 0.005clearance with an inlet temperature of 185 F. and an outlet temperatureof 104 F. at a rate of 20 lbs./ minute. The grease is then mixed withpump recycle bypassing the mill for an additional 30 minutes. Thesamples were drawn at 176 F.

EXAMPLE IV Two batches of 7:1 molar ratio calcium acetate/mixed fattysoap greases having the following compositions were prepared.

20 Inlet Temperature, F

25 the Colloid Mill (Sample No. 1008).

Table V Calcium Acetate, Wt.

percent 15.0 Calcium Soap, Wt. percent 8. 2 5 Moisture, Wt. percent 0.15Free CaO, Wt. percent 0.01

Sample No 100 100A 100B 1000' Sample Colloid 100A Unmilled Milledcolloid Recycle grease (once milled a milled through) second time ASTMPentrations, mm./10: Unworked 298 100 183 274 Worked (60 strokes) 280253 230 273 Recycle Colloid Milling Conditions:

N o. 3 Charlotte, 0.005 Clearance lbs/min. rate, 15 minutes- OutletTemperature, F 190 Additional Kettle Mixing, minutes In Table V, it isto be noted that a large spread between unworked and worked penetrationsstill exists even after a second pass through the high shearhomogcnizcr, However, when a low shear processing treatment followed theinitial high shear rate homogenizing, there resulted a small spreadbetween the unworked and worked consistencies Components, lbs. SampleSample 30 (Sample NO. 100C).

N098 00-99 It can be readily seen in Examples I through V that thesmooth texture obtained in the high shear homoge- Gmcml Acme Acid 3%nization was retained following the low shear homogeniza- 12.s2 6.44tion step while the spread between the unworked and 2313 22:8 workedconsistencies was reduced.

It is claimed: 1. A process for the preparation of a lubricating greaseThe greases were treated as shown in Table IV, consisting essentially ofan oil of lubricating viscosity Table IV Calcium Acetate, Wt. Percent--.14. 1 13. 7 Calcium Soap, Wt. Percent 7. 7 7. 5 Moisture, Wt. Percent0.6 0.6 Free CaO, Wt. Percent 0.08 0.07

Sample N 0. 8011 98 08A 98B* 99 99A 99B Unmilled Colloid RecycleUnmilled Colloid Recycle grease milled milled grease milled milled ASTAIPenetrations:

Unworked 312 192 267 319 198 288 Worked Strokes) 277 239 264 289 248 276Recycle Colloid Milling Conditions:

No. 3 Charlotte, 0.005 Clearance 20 lbs./

minute rate, 20 minutes:

Inlet. F 180 175 Du et, F 191 187 Additional Kettle Mixing, Minutes 3030 EXAMPLE V A 5.5 :1 molar ratio calcium acetate/mixed fatty soapgrease having the following composition was prepared.

Components, lbs.:

Glacial acetic acid. 48.0 Emery coconut acid (chiefly lauric) 25.6Hydrogenated castor oil 6.4 Hydrated lime 35.25

and a grease thickening amount of a mixed salt-soap thickener consistingessentially of an alkaline earth metal salt of acetic acid and analkaline earth metal soap of a higher molecular weight carboxylic acidof about 7 to 30 carbon atoms, wherein said salt of acetic acid and said430 SUS/ 100 F, M.C. neutral 320.0 sufficient to obtain a dispersion ofthe thickener, followed by shearing said grease at a rate in the rangeof about 1 to 500 reciprocal seconds to obtain a final greasecomposition.

2. The process of claim 1 wherein the higher molecular weight carboxylicacid is selected from the group consisting of carboxylic acidscontaining about 12 to 30 carbon atoms, carboxylic acids containingabout 7 to 12 carbon atoms and combinations of the same.

3. The process of claim 1 wherein the initial homogenization of themixed salt-soap thickened grease is conducted in the range of about10,000 to 200,000 reciprocal seconds.

4. The process of claim 1 wherein the second homogenization of the mixedsalt-soap thickened grease is conducted in the range of about 1 to 300reciprocal seconds.

5. A process for the preparation of a lubricating grease consistingessentially of an oil of lubricating viscosity in amounts of about 50 to95% of final composition and about 5 to 50 weight percent of a mixedsalt-soap thickener consisting essentially of an alkaline earth metalsalt of acetic acid and an alkaline earth metal soap of a highermolecular weight carboxylic acid of about 7 to 30 carbon atoms whereinsaid salt of acetic and said soap of a higher molecular weight acid arein a molar ratio of about 3 :1 to 20: 1, the improvement which consistsessentially of shearing said grease at a rate in the range or about 5000to 500,000 reciprocal seconds, suflicient to obtain a dispersion of thethickener and a spread between unworked and 60 stroke worked penetrationof about to 75 mm./ 10 followed by shearing said grease at a rate in therange of about 1 to 500 reciprocal seconds to obtain a greasecomposition having a maximum spread between unworked and 60 strokeworked penetration of about 15 mm./ 10.

6. The process of claim 5 wherein the higher molecular weight carboxylicacid is selected from the group consisting of carboxylic acidscontaining about 12 to carbon atoms, carboxylic acids containing about 7to 12 carbon atoms and combinations of the same.

7. The process of claim 5 wherein the initial homogenization of themixed salt-soap thickened grease is conducted in the range of about10,000 to 200,000 reciprocal seconds.

8. The process of claim 5 wherein the second homogenization of the mixedsalt-soap thickened grease is conducted in the range of about 1 to 300reciprocal seconds.

References Cited in the file of this patent UNITED STATES PATENTS2,850,458 Beerbower et a1 Sept. 2, 1958 2,973,321 Morway et al Feb. 28,1961 2,976,242 Morway Mar. 21, 1961

1. A PROCESS FOR THE PREPARATION OF A LUBRICATING GREASE CONSISTINGESSENTIALLY OF AN OIL OF LUBRICATING VISCOSITY AND A GREASE THICKENINGAMOUNT OF A MIXED SALT-SOAP THICKENER CONSISTING ESSENTIALLY OF ANALKALINE EARTH METAL SALT OF ACETIC ACID AND AN ALKALINE EARTH METALSOAP OF A HIGHER MOLECULAR WEIGHT CARBOXYLIC ACID OF ABOUT 7 TO 30CARBON ATOM, WHEREIN SAID SALT OF ACETIC ACID AND SAID SOAP OF SAIDHIGHER MOLECULAR WEIGHT CARBOXYLIC ACID ARE IN A MOLAR RATIO OF ABOUT3:1 TO 20:1, THE IMPROVEMENT WHICH CONSISTS ESSENTIALLY OF SHEARING SAIDGREASE AT A RATE IN THE RANGE OF ABOUT 5,000 TO 500,000 RECIPROCALSECONDS SUFFICIENT TO OBTAIN A DISPERSION OF THE THICKENER, FOLLOWED BYSHEARING SAID GREASE AT A RATE IN THE RANGE OF ABOUT 1 TO 500 RECIPROCALSECONDS TO OBTAIN A FINAL GREASE COMPOSITION.